Agroforestry for sustainable bioenergy and improved soil fertility in two agro-ecological zones, Rwanda
| dc.contributor.author | Uwingabire, Solange | |
| dc.date.accessioned | 2026-02-17T08:08:43Z | |
| dc.date.available | 2026-02-17T08:08:43Z | |
| dc.date.issued | 2024 | |
| dc.description | Dissertation | |
| dc.description.abstract | In Rwanda, the demand for food and energy is high and rising due to population growth. Furthermore, in rural households, the primary energy supply is from fuelwood combusted in inefficient cookstoves, resulting in fuel wastage and health issues associated with smoke in the kitchen. Biochar produced in cooking stoves can contribute to negative carbon emissions through sequestration of biomass Carbon while also providing other benefits for sustainable development, including provision of clean renewable energy and increased yields in tropical agriculture. In addition, B has low nutrient content and is recalcitrant to biodegradation; supplementing B with a fast-releasing nutrient source may contribute to improving soil fertility and physical conditions and lead to increased crop productivity. The reported research aimed to assess the impact of introducing Biochar-producing cooking stoves on household energy access and vegetable production, both on smallholder farms and experimental stations, in two agro-ecological zones (AEZs) of Rwanda. Participatory research on B production and use was conducted with 60 smallholder farmers selected purposively to evaluate the potential of Biochar – producing cooking stoves to address the interconnected challenges of household energy access and low vegetable productivity in Rwanda. The study compared two top-up lift draft (TLUD) gasifier types (Gastov and Karundura) with a three-stone fire (TSF) cookstove, using a standardized cooking test (SCT) and a household survey. Key indicators included cooking time, firewood usage and Biochar yield while the survey collected informationii about fuel availability, frequency of use, gasifier design, benefits and challenges. In addition, a three-season field study was done in two AEZs to assess the Biochar effects on vegetable yields after application to soil, where Biochar from gasifier stoves was applied in furrows (2-3 cm deep) in the gardens of French beans (Phaseolus vulgaris) at a rate of 3 tons per hectare (t/ha) using randomized paired design. Yield and the soil’s physical and chemical properties were analyzed. Concurrently, another, three- season field study (on station trials) was conducted in two AEZs to assess the synergistic effect of five types of Biochar (from S. sesban, G. sepium, A. angustissima, Eucalyptus, and Grevillea sp.) alone or mixed with livestock manure (LM) and applied at 1 and 3 t/ ha using French bean as a test crop. The key indicators were French bean yields, and soil chemical properties of soils. The study utilized descriptive statistics, one-way analysis of variance (ANOVA) using a generalized model in R, linear fixed effect model and the difference between means was examined using Tukey’s test at p<0.05. The study revealed that the TSF stove cooked a standardized meal faster than the gasifier stove did but the later reduced fuelwood consumption by 25-50% and produced biochar. The household survey responses revealed low firewood availability, but with the ability of firewood, savings when using gasifier stove. Gasifier stoves provided benefits through temperature control, reduced need for constant supervision, Biochar production, and reduced time needed for fuelwood collection, more hygienic and attractive appearance cooking. Most household cooks reported that the gasifier stoves produced less smoke and were safer for children and women’s health. The findings from on-farm trialsiii showed a consistently positive response in French bean yield following a one-time application of B in both sites. The B-treated plots were significantly (P<0.05) higher in pH, plant available nutrients (available Phosphorus (P), total Nitrogen (TN) and exchangeable bases), and soil nutrient retention capacity (high cation exchange capacity (CEC)). Soil porosity, plant available water (PAW), were significantly increased by B application while reducing soil bulk density (BD). The B produced by the TLUD gasifiers was perceived as positive as it combines B production and bioenergy, reduces off-farm biomass gathering, improves energy security and produces sufficient B to improve soil productivity in home gardens. For the on-station trials, the seasonal increase in yield has been recorded in combined plots with the high yield found in B-LM, each at the level of 3 t/ha, compared to the sole application of LM or B and the control treatment. The main factors for the increase of the French bean yield in the study areas are improved soil properties, including high pH; high nutrients content (Avail P, TN), soil OC and soil CEC. The application of B, either alone or in combination with LM, positively increased soil nutrients and French bean yield. The improvement became better as the B rate increased and when mixed with LM than sole application of B or LM. Increased vegetable yield enables enhanced nutrition and/or market opportunities and the adoption of the TLUD stoves may contribute to energy sustainability through the reduction of fuel use. The study recommends considering the combination of B with LM as an effective land rehabilitation strategy to improve soil fertility and increase vegetable yield in Rwanda. This technology of using B and LM is a low-cost technology foriv managing acidic sandy soils of Rwanda. The technology offers significant contributions in terms of improving soil fertility, increasing bioenergy output, mitigating climate change by sequestering atmospheric carbon in the soil and reducing greenhouse gas emissions associated with traditional cooking methods, particularly for women and children, thus improving the overall well-being and socio-economic stability of rural communities. | |
| dc.description.sponsorship | Swedish International Development Agency through Reforest Africa for its grant (n 0 13394) | |
| dc.identifier.uri | https://www.suaire.sua.ac.tz/handle/20.500.14820/7336 | |
| dc.language.iso | en | |
| dc.publisher | Sokoine University of Agriculture | |
| dc.subject | TLUD | |
| dc.subject | three-stone fire cookstove | |
| dc.subject | fuel saving | |
| dc.subject | cooking time | |
| dc.subject | Biochar | |
| dc.subject | soil properties | |
| dc.subject | French bean yield | |
| dc.subject | smallholder farmer | |
| dc.subject | Rwanda. | |
| dc.title | Agroforestry for sustainable bioenergy and improved soil fertility in two agro-ecological zones, Rwanda | |
| dc.type | Thesis |